Very small to large strains properties of a silty sand were measured at several water contents ranging from a few percents to saturation, using three triaxial devices with different types of transducers. In the analysis of the data, attention was focused on the influence of water content on the maximum (Young’s) modulus, the decay of modulus with strain, the effect of the confining stress, etc. Isotropic and triaxial tests, with measurement of negative pore water pressure, were performed on the same material. The effective stress concept, validated by a recent theoretical analysis by Coussy and Dangla (2002), was used to interpret the results. The predictions of a micromechanical model are compared with the experimental data in the elastic domain and on the failure criterion. The method highlights a simple way to relate the strength and stiffness of the soil to its negative pore water pressure.